Unravelling effects of cooperative adaptive cruise control deactivation on traffic flow characteristics at merging bottlenecks
Unravelling effects of cooperative adaptive cruise control deactivation on traffic flow characteristics at merging bottlenecks
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DOI：
10.1016/j.trc.2018.10.008
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发表时间：
2018-11
期刊：
影响因子：
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通讯作者：
Lin Xiao;M. Wang;W. Schakel;B. Arem
中科院分区：
文献类型：
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作者：
Lin Xiao;M. Wang;W. Schakel;B. Arem
协作自适应巡航控制(CACC)系统具有增加道路通行能力和缓解交通拥堵的潜力，这要归功于车间通信实现的较短的跟随距离。然而，由于CACC系统的加速和减速能力有限，当条件不在运行设计领域时，将发生停用并切换到ACC或人为驱动模式。由于缺乏关于这种相互作用的精细模型，现有的CACC交通流模型还不能再现真实的CACC车辆行为，并且很少考虑系统停用对瓶颈处交通流的影响。这项研究旨在通过使用一个现实的CACC模型来了解CACC在合并瓶颈时对高速公路运营的影响。该模型捕捉了驾驶员与系统的交互作用和字符串长度限制。我们对不同的CACC市场渗透率(MPR)进行了系统的交通仿真，得出了合并段的自由流能力和排队排泄率，并将其与均匀管道段的能力进行了比较。结果表明，增加CACC MPR确实可以提高道路通行能力。然而，合并瓶颈中产生的容量远远低于管道容量，并且在所有CACC MPR级别的瓶颈情况下，容量下降持续存在。研究还发现，由于在不同运行模式之间的切换，CACC增加了流动的非均质性。通过对CACC运行模式和运行轨迹的微观研究，揭示了CACC失活、交通拥堵和流量非均质性之间的密切关系。
Cooperative Adaptive Cruise Control (CACC) systems have the potential to increase roadway capacity and mitigate traffic congestion thanks to the short following distance enabled by inter-vehicle communication. However, due to limitations in acceleration and deceleration capabilities of CACC systems, deactivation and switch to ACC or human-driven mode will take place when conditions are outside the operational design domain. Given the lack of elaborate models on this interaction, existing CACC traffic flow models have not yet been able to reproduce realistic CACC vehicle behaviour and pay little attention to the influence of system deactivation on traffic flow at bottlenecks. This study aims to gain insights into the influence of CACC on highway operations at merging bottlenecks by using a realistic CACC model that captures driver-system interactions and string length limits. We conduct systematic traffic simulations for various CACC market penetration rates (MPR) to derive free-flow capacity and queue discharge rate of the merging section and compare these to the capacity of a homogeneous pipeline section. The results show that an increased CACC MPR can indeed increase the roadway capacity. However, the resulting capacity in the merging bottleneck is much lower than the pipeline capacity and capacity drop persists in bottleneck scenarios at all CACC MPR levels. It is also found that CACC increases flow heterogeneity due to the switch among different operation modes. A microscopic investigation of the CACC operational mode and trajectories reveals a close relation between CACC deactivation, traffic congestion and flow heterogeneity.